This invention relates to stabilizers for rubbers and is particularly concerned with the production of ring alkylated diphenyl-para-phenylenediamines as stabilizers for oxidizable diene rubbers.
The deleterious effects of ozone and oxygen on rubber articles is well-known and many antiozonants and antioxidants have been prepared which are capable of protecting various rubber compositions from the deleterious effects of ozone and oxygen. Many phenolic compositions and amine compositions have been used as antioxidants for rubber for a considerable period of time.
One of the more widely accepted stabilizers in the industry at present is diaryl-para-phenylenediamine as disclosed by Ronald Spacht in U.S. Pat. No. 3,432,460. The present invention relates to an improved method for the production of stabilizers disclosed in U.S. Pat. No. 3,432,460. The teachings of U.S. Pat. No. 3,432,460 are herein incorporated by reference.
As disclosed in U.S. Pat. No. 3,432,460 diaryl-para-phenylenediamines have been used as antiozonants and antioxidants for rubber, however, compounds of this class are in general solids which completely melt at temperatures in the neighborhood of 100.degree. C. or higher and which have only limited solubility in aqueous mediums and aliphatic hydrocarbons, and particularly rubber. They are thus quite difficult to incorporate in rubber without employing comparatively high temperatures, aromatic solvents, or vigorous milling action. Particular difficulties are encountered when incorporating high melting diaryl-para-phenylenediamines in latices and raw polymers.